I think there are 2 main benefits: 1.) Maintainability. Promote re-use of selectors and organization of your css files. I find that CSS gets sloppy very quickl

I think there are 2 main benefits: 1.) Maintainability. Promote re-use of selectors and organization of your css files. I find that CSS gets sloppy very quickly and there will be lots of non-DRY, redundant selectors, as well as legacy selectors that no one will ever remove because "what if something is still using it?" Your css files will slowly get larger and larger, and never smaller. This leads to the next point. 2.) Smaller file size. Less bandwidth used, faster requests. Yahoo has done a ton of research on the benefits of performant web apps: http://developer.yahoo.com/performance/rules.html http://developer.yahoo.com/performance/rules.html